Optoelectronic components that generate light radiation may be realized in the form of QFN packages (Quad Flat No Leads). There are disadvantages associated with traditional production of such components.
A leadframe comprising connection pads and web-shaped connecting structures is usually provided. For this purpose, a carrier composed of copper is structured. This may be carried out by masking carrier regions with a photoresist and etching. The structured leadframe is furthermore provided with an expensive coating (for example, NiAg or NiPdAu) by electroplating. As a result, the leadframe is suitable for soldering and connecting bond wires. Although required only in bond and soldering regions, usually the entire leadframe is coated, which means a cost disadvantage. Alternatively, regions of the leadframe may be masked to coat the leadframe only locally (spot plating). This is complex and costly.
Furthermore, a molding compound is molded around the leadframe to form a molded body. The molded body comprises recesses via which the connection pads are exposed at a front side. At these locations, light-emitting semiconductor chips are arranged on the connection pads and electrically connected thereto. The rear sides of the connection pads likewise remain free to be able to solder the QFN components produced onto a circuit board. Further processes are filling the recesses with a potting compound, and singulating the component assemblage produced in this way.
In a process-governed manner, the connection pads may comprise residues of the molding compound at the front side. To avoid problems associated therewith when arranging the semiconductor chips, after the molding-around process, a cleaning step of removing the residues is usually carried out (deflashing). In this process, gaps may form between the leadframe and the molded body. Subsequently filling the recesses of the molded body may have the consequence that the potting compound used creeps through the gaps and the rear sides of the connection pads are contaminated as a result (seepage). This may cause soldering problems for the components. Preventive measures such as applying a rear-side film by adhesive bonding or applying a rear-side protective lacquer, or subsequently removing the residues of the potting compound, are complex and expensive.
Singulating involves severing, generally sawing, through an inhomogeneous material combination, i.e., the molded body and the web-shaped connecting structures of the copper leadframe. This limits the possible sawing speed to produce clean outer edges of the components. In that process, the intention is to avoid smearing material of the copper webs since short circuits may otherwise occur. In the singulated components, the copper webs reach the outer sides thereof and may therefore corrode.